1. Field of the Invention
The present invention relates to a lens housing that contains image-capturing lenses and lens frames adapted to move forward and backward.
2. Description of the Related Art
Conventionally, a zoom-lens housing has been proposed as a lens housing that contains movable frames in Japanese Unexamined Patent Publication No. 4-52628. The proposed zoom lens housing rotates inner and outer zoom rings about an optical axis to move all lens frames forwardly and backwardly in a direction corresponding to the optical axis. According to the forward and backward movement of the lenses, the focal length of the zoom lens is varied. Further, according to the forward and backward movement of the lenses caused by the outer zoom ring, the lens housing moves a focusing-lens-group frame forward and backward to perform focusing operations.
In the above zoom lens housing the focusing lens group is moved forward and backward by the outer zoom ring. A coupling member for coupling the outer zoom ring and the focusing-lens-group frame is formed of a slender plate. The coupling member receives not only simple thrusting forces but also torsional forces in the radial direction. Responsive to these forces, the outer zoom ring (which is a frame member) and the focusing-lens-group frame are deformed. The deformations cause problems in that smooth extending and retracting operations cannot be performed, and that the aforementioned coupling member is deformed.
Also, conventionally, a collapsible lens housing that contains image-capturing lenses and has movable frames (frame members) in an image-capturing region has been proposed in Japanese Unexamined Utility Model Publication No. 11-171412. The proposed lens housing also has relief grooves formed continuously in cam grooves of a cam cylinder, which engage with cam followers provided for reduction of an inter-lens-group distance when shifting the lens housing into a collapsed-barrel state. With this lens housing, the cam followers can be engaged with the relief grooves and increase lens extension.
However, in the lens housing proposed in the Japanese Unexamined Utility Model Publication No. 11-171412, in addition to the cam grooves for moving the movable frames through the cam cylinder, relief grooves must be provided. This requires extra space, restricting the shape of the movable frames and decreasing rigidity.